They are called codices,
codex is singular (meaning one). The Maya would write with quills
made from turkey feathers. When the Spanish came, they burned many
books. Only four remain today. It probably took several weeks
or more to write each codex.
Each image was first outlined with black ink made
of a coal base. The first drawing was done with a tool made from
the thorns of the maguey cactus or from chips and bones of small
animals including birds. Brushes were made of animal hair.
Using color to illustrate the codices was not done just for looks.
Colors and shades of colors meant a lot
The Maya gave a special meaning to each color, which they
related with gods, nature and the sky.
People thought the writers were in touch with the
gods. The codices were considered sacred. The books were kept in
special rooms inside temples and important buildings.